1. Field of the Invention
Embodiments of the present invention generally relate to downhole tools for a hydrocarbon wellbore. More particularly, this invention relates to a packer pressure control valve. More particularly still, this invention relates to a fracture valve with a latch mechanism and erosion resistant components.
2. Description of the Related Art
In the drilling of oil and gas wells, a wellbore is formed using a drill bit that is urged downwardly at a lower end of a drill string. When the well is drilled to a first designated depth, a first string of casing is run into the wellbore. The first string of casing is hung from the surface, and then cement is circulated into the annulus behind the casing. Typically, the well is drilled to a second designated depth after the first string of casing is set in the wellbore. A second string of casing, or liner, is run into the wellbore to the second designated depth. This process may be repeated with additional liner strings until the well has been drilled to total depth. In this manner, wells are typically formed with two or more strings of casing having an ever-decreasing diameter.
After the wellbore has been drilled and the casing has been placed, it may be desirable to provide a flow path for hydrocarbons from the surrounding formation into the newly formed wellbore. Perforations may be shot through the liner string at a depth which equates to the anticipated depth of hydrocarbons. In many instances, either before or after production has begun, it is desirable to inject a treating fluid into the surrounding formation at particular depths. Such a depth is sometimes referred to as “an area of interest” in a formation. Various treating fluids are known, such as acids, polymers, and fracturing fluids.
In order to treat an area of interest, it is desirable to “straddle” the area of interest within the wellbore. This is typically done by “packing off” the wellbore above and below the area of interest. To accomplish this, a first packer having a packing element is set above the area of interest, and a second packer also having a packing element is set below the area of interest. Treating fluids can then be injected under pressure into the formation between the two set packers through a “frac valve.” The “frac valve,” however, must also be opened prior to injecting the treating fluids.
A variety of pack-off tools and fracture valves are available. Several such prior art tools and valves use a piston or pistons movable in response to hydraulic pressure in order to actuate the setting apparatus for the packing elements or opening apparatus for the fracture valve. However, debris or other material can block or clog the pistons and apparatus, inhibiting or preventing setting of the packing elements or opening of the fracture valve. Such debris can also prevent the un-setting or release of the packing elements or the closing of the valve. This is particularly true during fracturing operations, or “frac jobs,” which utilize sand or granular aggregate as part of the formation treatment fluid. Further, the treating fluids may cause massive erosion of the fracture valve components, such as the valve ports, which may result in disruptive pressure drops across the tools.
Therefore, there is a need for an improved pack-off tool and fracture valve.